Duty cycle modulation is a technique in which pulses, or a relationship among pulses, in a pulse wave are varied to encode information or control power delivery to a load. The term “duty cycle” refers to the fraction of time a duty-cycle-modulated (DCM) signal is active high over some specified interval of time, often the time interval between consecutive rising edges of the pulse waveform. In general, duty cycle may be used to describe periodic, semi-periodic, and aperiodic DCM signals. In a periodic DCM signal, for example, the interval of time corresponds to the period of the signal, and the duty cycle is defined for each signal period as the fraction of time during which the signal is high.
DCM signals are generated in various ways. In one commonly-used approach, pulse widths of a signal are varied to produce the desired DCM signal. DCM signals generated using this approach are referred to as a “pulse width modulated” or “PWM” signals. In another approach the pulse widths are fixed but the times between pulses are varied to produce a DCM signal having a variable pulse density. DCM signals generated by this latter approach are referred to as “pulse density modulated” or “PDM” signals or, alternatively, “pulse-frequency modulated” or “PFM” signals.
There are various circumstances where it is necessary or it would be desirable to translate duty cycle information in DCM signals to higher frequencies or higher data rates. The present invention addresses these needs and desires.